Getting Started with Renesas Capacitive Touch Technology

Please can you tell me what is needed for me to design the Renesas Capacitive sensing technology into my application?

  • Capacitive Touch interfaces allows engineers to design superior HMI for their products which enables the user to accomplish a variety of tasks in an intuitive way, bringing out the full potential of today’s highly functional products.

    Renesas provides engineers with a dedicated IP Block on a selection of their MCUs to allow easy implementation of Capacitive Touch buttons, sliders and wheels.

    However, a Capacitive Touch design is certainly not limited to the IP Block on the MCU. It involves careful mechanical design of the product, care with sensor layout on the PCB, selection of overlay materials and software design. The flow diagram below is a representation of the workflow needed when undertaking a Capacitive Touch design for a product : 

    Firstly, determine how many buttons, sliders or wheels are needed in your design. Please use the guide below in order to determine the range of sensors available in the RX Family of MCU products :

    Please use the URL below to get further part and roadmap information :

    Touch Parts and Roadmap

     Now we need to understand the type of application you intend to run on the MCU. Will the application require a fast CPU in order to process many communications channels? Will large amounts of data need to be stored e.g. fonts, tables etc. Will a display be required?

    Once the Flash size, CPU frequency, communications channels etc are known, you can choose the part number for your MCU. Please use the Capacitive Touch Solution Brochure (R30CA0159EJ300) to help you with MCU selection.

    With the device chosen, you can now begin to design your Capacitive Touch interface. This is a complex process which involves multiple disciplines :

    The following application notes are applicable during this phase of development :

    Technology

    CTSU Basis of Cap touch detection  (R30AN0218EJ0100)

    Self Capacitance Touch Method (R30AN0216EJ0100 - available in Workbench6 document manager)

    Mutual Capacitance Touch Method (R30AN0217EJ0100 - available in Workbench6 document manager)

    CTSU Accuracy Enhancement (R01AN3610EJ0100)

    Software

    Please read the following Guide :

    Workbench6 User Manual (R20UT4247EJ0100)

    This guide will instruct you on software needed during development. The packages include :

    Renesas e2Studio (Eclipse based IDE)

    Renesas Workbench6 (Development and tuning tool)

    Renesas C Compiler Package for RX

    Python 2

    Visual C++ Run-time library (32-bit)

    Microsoft .NET framework 4.0 or later

    With this phase of the development complete you must construct a prototype in order to test the design prior to release for production :

    The following application notes are applicable during this phase of development :

    Design Guides (PCB Layout)

    Capacitive Touch Design Guide (R01AN3958EJ0100)

    Mutual Capacitance Key Design Guide (R30AN0219EJ0100)

    Mutual Touch Electrode Characteristics (R01AN3192EJ0100 - available in Workbench6 document manager)

    Wheel & Slider Design Guide (R01AN3421EJ0100 - available in Workbench6 document manager)

    Additional Layout Guidelines (R01AN3825EU0101)

    Water-resistance Layout Guide (R01AN3190EJ0100 - available in Workbench6 document manager)

    With the hardware constructed the tuning of the Capacitive Touch sensors can be carried out :

    The tuning tool used with Renesas Capacitive Touch technology is called Workbench6 :

    Please read the following Guide :

    Workbench6 User Manual (R20UT3986EJ0100)

    Renesas Workbench6 (Development and tuning tool)

    The tool communicates with the Renesas MCU via either the emulator interface, USB or UART channels.

    With the prototype board completed and tuned it must be tested. These tests are needed to ensure that the overall product passes the required noise tests (conducted immunity, ESD, EMI etc) and has the required margin to absorb manufacturing variations :

    If changes are required then the engineer is required to re-visit the design or develop the final production ready product: